Trays used to transfer items such as wafers, IC chips, electronic components and the like should have antistatic properties. Therefore, traditionally, such trays have been formed of plastic materials treated to have conductive properties, such as ABS resin mixed with antistatic agents, carbon black, carbon fiber, carbon nano-tubes and the like.
Antistatic agents, however, can be easily affected by humidity because of ion conductivity. Antistatic properties can also deteriorate over time as antistatic agents are lost through use or washing. In addition, polymers mixed with large amounts of antistatic agents can exhibit deteriorated physical properties such as heat resistance.
Carbon black is not affected by humidity, washing and the like. However, adding large amounts of carbon black is required to impart conductive properties, and the surface of the plastic article can become susceptible to scratches and abrasion. Accordingly the plastic article can exhibit reduced abrasion resistance and carbon particles can be easily lost from the article.
Carbon fiber resin can influence the properties of electrical parts since the particles can protrude from an exterior part of a plastic article and be broken off, and the resin per se has high strength. Additionally, when treating a head or an IC chip with ultrasonic waves, the products can be damaged by debris from the carbon fiber per se and/or resin debris from the carbon fiber surface, resulting from contact between particles.